Many gasoline service stations require the installation of multiproduct fuel dispensers or pumps, each for dispensing a plurality of different grades, or octane levels, of gasoline products at each fueling station. Conventionally, three different products are provided per fueling station, namely a high octane fuel, a medium octane fuel and a low octane fuel. Mixing of these various products can result in the dilution or lowering of the octane level of the high and medium octane fuels which can adversely affect the performance of the customer's automobile. Testing procedures have therefore been developed in the United States to certify the octane levels of the fuels dispensed from commercial fuel dispensers. The testing and certification procedures are set forth in the National Conference on Weights and Measures Publication No. 12, entitled “Examination Procedure Outlines for Weighing and Measuring Devices.” Pursuant to these testing guidelines, the person conducting the test is required to flush at least 0.3 gallons of fuel from the dispenser before taking the test sample. See page 57, fn. 1. Thus, in dispensers used at United States gasoline service stations, a slight mixing of the various fuel products of a multiproduct fuel dispenser may occur, so long as the contaminated product is flushed from the system during the first 0.3 gallons of discharge.
To minimize the mixing of the various products dispensed from a multiproduct fuel dispenser, known dispensers typically include a separate flow path for each product from its reservoir product tank which stores the fuel to the outlet nozzle which introduces the fuel into the consumer's automobile. These systems therefore require the duplication of the components disposed between the tank and the nozzle for each fuel product, including the flow meter. In this manner, however, no contamination of the octane level of the products can occur. Such dispensers are known as “wet hose systems” as the hose, as well as the flow meter and other delivery components, remain filled with fuel from the most recent use. Through the use of such separate hoses, meters, etc., dispensers of the prior art avoid contamination of fuel being dispensed at a particular time with fuel from a previous use that would otherwise remain in the system at the termination of the last dispensing cycle. Spalding, U.S. Pat. No. 5,332,011, a patent assigned to the assignee of the present invention, discloses such a dispenser, in which three nozzles, fuel hoses and flow meters, each for a different grade of gasoline, are combined in a single dispenser.
There are many disadvantages in the use of discrete delivery systems for each product fed through a multiproduct fuel dispenser. For example, the cost of such dispensers is increased due to the requirement for multiple hoses, nozzles and meters. Also, the overall size and space requirements of such a dispenser are increased due to the requirement to house the multiplicative components. In addition, and especially with respect to the flow meters, the cost of maintenance and repairs is increased for each discrete delivery system included in such dispensers.
In an effort to overcome some of the above problems, multiproduct fuel dispensers have been developed that comprise tri-axial fuel hoses having three concentric passages within a single hose that lead to a single nozzle. Such devices simplify operation for the consumer as there is only a single nozzle, but they do not alleviate the need for separate flow meters for each product or improve the maintenance and repair costs. Moreover, such devices might actually increase the cost of the dispenser due to the complexity of the tri-axial hoses.
Other multiproduct fuel dispensers have been developed in which the supply lines from each reservoir tank are manifolded into a single fuel hose downstream of the flow meter, which hose then leads to a single nozzle. Although this eliminates the multiplicity of nozzles and hoses, the problems associated with the multiplicity of flow meters, such as complexity, space limitations, and repair and maintenance expenses, remain.
What is needed is a multiproduct fuel dispenser that uses a common flow meter for dispensing a multiplicity of fuels.